Due to the advent of new technologies,devices and communication means like social networking sites,the amountof data produced by mankind is growinglyrapidly every year.The amount of data produced us from the beginning of time till 2003 was 5 billion gigabytes.”90% of the world’s data was generated in last few years”.Hadoop is designed to scale up from single server to thousands of machines, each offering local computation and storage.This paper conducts a detailed survey on existing technologies and emerging trends in hadoop for fast processing of petabytes of data within seconds.The technology is changing day by day.New trends in hadoop is popping up fastly.